The titanium containing catalyst of this invention is highly active and is suitable for polymerization of ethylene and other 1-olefins, particularly of 2-8 carbon atoms, and copolymerization of these with 1-olefins of 2-20 carbon atoms, such as propylene, butene and hexene, for example, to form copolymers of low- and medium-densities. It is equally well suited for particle form, gas phase and solution polymerization processes, and is especially effective in the selective production of high-density polyethylene having a narrow molecular weight distribution and high melt index for injection molding applications.
The catalyst of this invention has an enhanced sensitivity to molecular weight control by hydrogen. This makes it possible to make high melt index particle form polyethylene with less hydrogen and at a lower polymerization temperature. The catalyst is also well suited for the production of high-strength fibers or film having a low melt index.
The catalyst does not require an excess of titanium and therefore obviates the need for removal of catalyst residues from product polymer. The catalyst is suitable for use in particle form polymerization plants designed for prior silica-supported chromium oxide catalysts. Heretofore, titanium catalysts have not been extensively used in such plants due to the substantial excess of corrosive titanium compounds typically used in the preparation of such catalysts. The present catalyst is easily injected into particle form reactors by means of well known automatic feeding valves, and corrosion-resistant materials of construction are not required.
The most pertinent prior art known to me is as follows:
South Africa Appl. No. 69/3534, 10/5/69 by Van Den Berg and Tomiers of Stamicarbon describes catalysts made from organomagnesium compounds, alkyl aluminum chloride compounds, and titanium compounds which are increased in reactivity by the addition of alcohols. A support, or granular ingredient, is not used, there is no separation of the solvent, and the use of a cocatalyst is not part of the disclosure.
German Off. No. 2,721,058, Nov. 23, 1978 by Gunter Schweier et al. of BASF reveals a catalyst with a porous inorganic oxide like silica or silica-alumina as a support. A solution of a reaction mixture of an alcohol, a titanium trihalide, and a magnesium compound is added to the oxide, and then the solvent (i.e. the alcohol) is evaporated giving an intermediate solid product. This solid product is suspended in a solution of organometallic compound, which may be an alkyl aluminum or silicon halide compound. The suspended solid component may be used as is along with an organometallic compound as a cocatalyst. The suspended solid compound can also be filtered, and washed prior to use, and for gas phase polymerization it can be coated with wax. The magnesium compounds are not alkyl magnesium compounds but alkoxides and halides and other types of compounds. Another Schweier patent, German Off. No. 2,721,094 is similar to this one. It reveals that the silica or silica-alumina may be treated with an alkyl aluminum halide compound beforehand. U.S. Pat. No. 4,110,523, Aug. 29, 1978, also by Schweier et al. covers a similar catalyst. In this case, the treatment with the alkyl aluminum or silicon halide solution is eliminated.
U.S. Pat. No. 4,130,699, Dec. 19, 1978 by G. R. Hoff and Peter Fotis of Standard Oil discloses a supported catalyst for vapor phase polymerization which are made less active prior to feeding to the reaction vessel by treatment with alcohols, acetates, ketones, aldehydes, or esters.
U.S. Pat. No. 4,105,585, Aug. 8, 1978 by Ian Matheson of BP Chemicals describes a catalyst prepared from the reaction of magnesium powder, a titanium halide and alcohol.
U.S. Pat. No. 3,647,772 by N. Kashiwa (Mitsui Petrochemical, May 7, 1972) involves treating anhydrous magnesium carbonate with polar organic compounds including alcohols. When this is done, more titanium from titanium tetrachloride can be fixed upon the magnesium carbonate. Catalyst reactivity, melt index and bulk density of the product are increased by the treatment with the polar organic compound.